About a century ago, scientists discovered that most of our brain cells formed during fetal development persist throughout life. But this discovery stimulated other scientists to discover the age of cells throughout the human body. If we look at the adult human body at age 40 from head to toe, the list goes something like this:

Brain cells of the cerebral cortex (the grey matter) are with you from birth.

Brain cells of the visual cortex (the array of cells in the front of the brain used for vision) are with you from birth.

Brain cells of the cerebellum (the structures at the base of the brain) are slightly younger than you are.

Intercostal muscle cells are about 15.1 years old.

Gut lining cells are about 5 days old.

Gut cells other than the lining are about 15.9 years old.

Skin cells are about 14 days old.

Red blood cells are about 120 days old.

Bone cells are about 10 years old.

We do not know precisely the average ages of eye-lens cells, heart cells, liver cells, pancreas cells, fat cells, and bone marrow cells.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au